In the RTK measurements, a centering rod of a rover should be vertically placed, and then the position coordinate of the to-be-measured point on the ground is calculated according to the position of the phase center of the antenna of the Global Navigation Satellite System (GNSS) receiver and the distance from the phase center to the ground. However, in the practical measurement operation, due to the impacts of the topographic conditions and the restrictions of the instrument itself, the centering rod of the rover cannot be vertically placed in many measurement points, and an inclination is usually required, thereby causing a complicated measurement process and a large measurement error.